Ryan Ingram wrote:
More FRP stuff: a new type for Future that came to me in an inspiration this morning. But it's ugly and I need someone with better theoretical underpinnings than me to tell me what I've really built :)
data Future t a = Known t a | Unknown (t -> IO (STM (Maybe (Future t a))))
This is a composition of (applicative) functors. Not sure whether this helps from the theoretical side, but it can be used to considerably shorten your code: type Tower t b = t -> IO (STM (Maybe b)) fmap4 :: (a -> b) -> Tower a -> Tower b fmap4 f = fmap . fmap . fmap . fmap $ f delayF :: Ord t => t -> Future t a -> Future t a delayF t0 (Known t a) = Known (max t0 t) a delayF t0 (Unknown f) = Unknown $ fmap4 (delayF0 t0) f instance (Ord t, Bounded t) => Monad (Future t) where return = Known minBound Known t a >>= g = delayF t (g a) Unknown f >>= g = Unknown $ fmap4 (>>= g) f Regards, apfelmus